The present invention relates to a seal arrangement for sealing two machine elements.
A multiplicity of sealing problems arise in hydraulic and pneumatic machines and devices. The designer sets different requirements on a seal arrangement according to the envisaged use. Such demands include, that the seal arrangement takes up little space and is easily assemblable. Furthermore, the seal arrangement should seal well and have a long life in the envisaged pressure and temperature range. In case the seal arrangement serves for the sealing of a gap between two parts moving relative to one another, the seal arrangement should cause only the smallest possible friction during the motion and also result in little static friction. Otherwise, there is the danger that, for example in the case of hydraulic cylinders, the pistons on starting out of the rest position will not move uniformly, but jerkily (stick slip).
When a seal arrangement is provided perhaps for the sealing of a piston in a hydraulic cylinder for a great pressure range of, for example, 0 to 500 bar, it should have different properties which are in part opposed to one another. The seal arrangement should be easily deformable so that it closes off well at small pressures and when used with stationary parts, but nevertheless should slide easily on displacement of the piston. Also at high pressures it should not be pressed into gaps present because of the required play between the machine parts to be sealed.
Different kinds of seal arrangements are known which only partially fulfil various requirements. For example, a seal arrangement is known which comprises two rings for insertion into an annular groove of a piston arranged in an hydraulic cylinder. The one, inner, ring of the seal arrangement consists of an elastomer and bears by its inside surface against the base of the annular groove. The other, outer, ring consists of polytetrafluoroethylene and bears by its inside surface against the outside surface of the elastomer ring. The outer surface of the outer ring bears against the inside surface of the hydraulic cylinder. This known seal arrangement is quite well suited for oil at high pressure. At low pressures and particularly with gaseous flow media, it affords incomplete sealing due to the small elasticity of the polytetrafluoroethylene.
An object of the present invention is to provide a seal which is usable at high as well as also at low pressures and for liquids as well as for gases.